Hundreds of pro-independence supporters in Catalonia are protesting outside a courthouse to demand the release of regional government officials arrested in a crackdown by Spanish authorities over a planned secession referendum.

The protest Friday in the northeastern Catalan town of Hospitalet de Llobregat is an extension of another started Thursday outside the Catalan judiciary headquarters in nearby Barcelona that attracted thousands. A pro-independence group says that about 2,500 supporters were attending the protest in Hospitalet.

Many of the demonstrators in Barcelona had slept overnight near the judiciary building in tents or hammocks strung up between lampposts.

The Catalan National Assembly civic group has called for the protests to continue until the near dozen officials detained Wednesday are released.

Spain’s interior ministry said on Friday it was sending more state police to Catalonia to maintain order and make sure the banned referendum on independence does not take place.

A man holds a placard reading “Vote yes” in front of Spanish policemen during a demonstration in Barcelona on September 20, 2017. (Photo by AFP)

Catalonia has its own police called Mossos d’Esquadra, though the state police Guardia Civil has quarters throughout the region and often works alongside them.

The interior ministry has not disclosed how many more police officers it is sending to the region but Spanish media said between 3,000 and 4,000 had already arrived or were on their way.

They would join the roughly 5,000 state police normally stationed in Catalonia and around 17,000 Mossos officers.

“They will be tasked with surveillance of public space and maintaining order and they will act in case the illegal referendum is maintained,” the interior ministry said in a statement.

They will act as a backup for the Mossos, who will remain in charge, it added.

Some are billeted in three ferries rented by the Spanish government and moored in the harbors of Barcelona and Tarragona because of both a shortage of temporary housing and to avoid clashes between protesters and police forces.

The interior ministry has told police in Catalonia they will not be able to take time off between Sept. 20 and Oct. 5.

The Catalan government earlier this week accused the Spanish authorities of effectively taking over its administration after state police raided its offices and arrested officials, and the finance ministry took control of the local finance department.

The Catalan regional leader Carles Puigdemont on Thursday said he would press on with the referendum, flouting a court ban, as tens of thousands gathered for a second day on the streets of Barcelona demanding the right to vote.